A continued change of gate-controlled-diode characteristics of n-MOSFETs following hot-carrier injection is observed. It is also observed that the post-stress gate-controlled-diode characteristics can be altered by the electrical measurement itself. It is found that the instabilities in the gate-controlled-diode characteristics are due to the change of gate current in the post-stress period. This current increases with both the stress time and the post-stress time but is reduced by the measurement itself. These phenomena can be explained by a model which is based on the release of hydrogen ions by thermal detrapping of the trapped holes in the gate oxide.